GATE ECE
Electronic Devices and VLSI
Semiconductor Physics
Previous Years Questions

Marks 1

Consider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is 1017 cm$$-$$3 and the intrinsic carrier concen...
In a non-degenerate bulk semiconductor with electron density n = 1016 cm$$-$$3, the value of EC $$-$$ EFn = 200 meV, where EC and EFn denote the botto...
Select the CORRECT statements regarding semiconductor devices
A bar of Gallium Arsenide (GaAs) is doped with Silicon such that the Silicon atoms occupy Gallium and Arsenic sites in the GaAs crystal. Which one of ...
A small percentage of impurity is added to an intrinsic semiconductor at 300 K. Which one of the following statements is true for the energy band diag...
An n–type silicon sample is uniformly illuminated with light which generates 1020 electron hole pairs per cm3 per second. The minority carrier lifetim...
A piece of silicon is doped uniformly with phosphorous with a doping concentration of $$10^{16}/cm^2$$. The expected value of mobility versus doping c...
A silicon sample is uniformly doped with donor type impurities with a concentration of $$10^{16}/cm^3$$.The electron and hole mobilities in the sample...
In the figure ln(ρi) is plotted as a function of 1/T, where ρi the intrinsic resistivity of silicon, T is is the temperature, and the plot is almost l...
The cut-off wavelength (in µm) of light that can be used for intrinsic excitation of a semiconductor material of bandgap Eg= 1.1 eV is ________. ...
A thin P-type silicon sample is uniformly illuminated with light which generates excess carriers. The recombination rate is directly proportional to
At T = 300 K, the hole mobility of a semiconductor $$\mu_p\;=500\;cm^2/V-s$$ and $$\frac{kT}q\;=\;26\;mV$$.The hole diffusion constant Dp in cm2/s is_...
Drift current in the semiconductors depends upon
Which of the following is true?
Under low level injection assumption, the injected minority carrier current for an extrinsic semiconductor is essentially the
The concentration of minority carriers in an extrinsic semiconductor under equilibrium is:
The primary reason for the widespread use of Silicon in semiconductor device technology is
A Silicon PN junction at a temperature of 20°C has a reverse saturation current of 10 pico-Amperes (pA). The reverse saturation current at 40°C for th...
The band gap of Silicon at room temperature is:
The impurity commonly used for realizing the base region of a silicon n-p-n transistor is
n-type silicon is obtained by doping silicon with
The band gap of silicon at 300 K is
The intrinsic carrier concentration of silicon sample at 300oK is $$1.5\times10^{16}/m^3$$. If after doping, the number of majority carriers is $$5\ti...
The units of $$\frac q{KT}$$ are
The probability that an electron in a metal occupies the Fermi-level at any temperature (> 0 K)
The drift velocity of electrons in silicon
In a P-type silicon sample, the hole concentration is $$2.25\times10^{15}/cm^3$$. If the intrinsic carrier concentration is $$1.5\times10^{15}/cm^3$$ ...
A p-type silicon sample has a higher conductivity compared to an n-type sample having the same dopant concentration.
A small concentration of minority carries is injected into a homogeneous semiconductor crystal at one point. An electric field of 10 V/cm is appl...

Marks 2

The dependence of drift velocity of electrons on electric field in a semiconductor is shown below. The semiconductor has a uniform electron concentrat...
A dc voltage of 10V is applied across an n–type silicon bar having a rectangular cross–section and a length of 1cm as shown in figure. The donor dopin...
Consider a silicon sample doped with ND = 1×1015/cm3 donor atoms. Assume that the intrinsic carrier concentration ni = 1.5×1010/cm3. If the sample is ...
An N-type semiconductor having uniform doping is biased as shown in the figure. If EC is the lowest energy level of the conduction band, EV is the h...
Assume electronic charge q = 1.6×10-19 C, kT/q = 25 mV and electron mobility μn = 1000 cm2/V-s. If the concentration gradient of electrons injected in...
The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge...
The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge...
A silicon sample 'A' is doped with 1018 atoms/cm3 of Boron. Another sample 'B' of identical dimensions is doped with 1018 atoms/cm3 of Phosphorus. The...
The electron concentration in a sample of uniformly doped n-type silicon at 300oK varies linearly from $$10^{17}/cm^3$$ at x = 0 to $$6\times10^{16}/c...
An n-type silicon bar 0.1 cm long and $$100\;\mu m^2$$ in cross-sectional area has a majority carrier concentration of $$5\times10^{20}/m^3$$ and the ...
A semiconductor is irradiated with light such that carriers are uniformly generated throughout its volume. The semiconductor is n-type with $$N_D=10^{...
A silicon sample is uniformly doped with 1016 phosphorous atoms/cm3 and 2 ×1016 boron atoms/cm3. If all the dopants are fully ionized, the material is...
In an intrinsic semiconductor the free electron concentration depends on
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